DIFFERENTIAL PROTECTIVE RELAY APPARATUS

摘要

In an apparatus for differential-protection of a bus bar having a plenty of terminals which includes a plurality of trunk lines, an impedance of a differential circuit connected in parallel to a current transformer provided in each of the terminals is changed depending on either a terminal voltage of this differential circuit, or another terminal voltage derived from a part of the impedances. Then, either a high impedance differential relay, or a low impedance differential relay is selectively available so as to confirmly detect a fault in the bus bar.